Ductwork return air question or two

 
cabinover
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Post by cabinover » Fri. Dec. 08, 2017 5:49 pm

If this is in the wrong forum mods please feel free to move it. I have an air handler under my home (double-wide) that keeps the temps in here cozy. The return right now is two 7" pieces of flex duct through my closet floor. That creates a little problem in that our room is stupid hot.

I haven't been down to measure the opening of said air handler but I think it's about 20X20 or so. In talking with a friend today he said to just put a return in the wall, center of the house and duct down the wall to underneath, then to the air handler. The wall is 4". That means a 3 1/2" X 14" duct.
When I asked "won't that be the bottleneck in moving air?" he said no it wouldn't. It would move through that faster but still get the same CFM as say an 8X16 duct would.

I just don't see it happening that way and think the wall duct would choke the air flow. Am I correct or not? Thanks


 
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Lightning
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Post by Lightning » Fri. Dec. 08, 2017 7:24 pm

Well you can look at it from a surface area perspective
3.5 × 14 = 49 sq in of area

To find the area of your current arrangement
A = pie × radius squared
A = 3.14 × 3.5 × 3.5
A = 38.5 sq in

And there are two of them
So that's 77 sq in total.

Seems your current arrangement is capable of more volume of air flow by about 50%

 
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Post by cabinover » Fri. Dec. 08, 2017 7:52 pm

That makes sense. I really just need to move the intake somewhere else towards the center of the house to take care of my problem. Or...two wall grates next to each other. Would love one of the old time large cold air floor returns but the wife says no to cutting up her Maple floor in the living room.

 
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Post by windyhill4.2 » Fri. Dec. 08, 2017 8:27 pm

Some of the old houses had "grills" in the walls,they were somewhere about 8-12" square. If you used 2 wall stud spaces with those grills,you would likely have enough flow.
OR,try doing 1 wall stud spacing grill in the hallway,delete 1 in your bedroom & try it that way. You can always add 1 or delete1 later.

 
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Post by McGiever » Sat. Dec. 09, 2017 8:52 am

Can not tell you all is equal when it's not.

Can tell you most air handlers have 2 or 3 fan speeds, if slowing fan helps.

Then there's the possibility to raise the return grill up to ceiling....momma ain't giving up any closet space though, is she?

 
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Post by samhill » Sat. Dec. 09, 2017 9:02 am

Not at all an expert but it seems like an odd place to put a return inside a closet, if most women are like the one's I know there would be stuff blocking the return. If the closet doors have slats in them or left open at night it may help.

 
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Post by Lightning » Sat. Dec. 09, 2017 1:16 pm

I'm a little confused why having the return in your room makes the room hot. How close is the closest warm air supply register?


 
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Post by windyhill4.2 » Sat. Dec. 09, 2017 1:45 pm

Lightning wrote:
Sat. Dec. 09, 2017 1:16 pm
I'm a little confused why having the return in your room makes the room hot. How close is the closest warm air supply register?
Really ?? :roll:

When the cold air return draws the cold air from the room... :arrow:

HOT air replaces it. :clap:

THAT is why the bedroom gets too hot. :)

Especially since this would appear to be the only cold air return for the system. :what:

 
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Post by Lightning » Sat. Dec. 09, 2017 2:03 pm

Well the cold air return is suppose to return cold air lol. My cold air return doesn't create a warm area around it, why is his? I also only have one cold air return and the room it's in isn't any warmer than any of the others, in fact it's cooler.

That's why I was wondering how close the closest warm air supply register is.

 
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Post by windyhill4.2 » Sat. Dec. 09, 2017 2:12 pm

Lightning wrote:
Sat. Dec. 09, 2017 2:03 pm
Well the cold air return is suppose to return cold air lol. My cold air return doesn't create a warm area around it, why is his? I also only have one cold air return and the room it's in isn't any warmer than any of the others, in fact it's cooler.
Say what ??? :what:
WOW !!

Of all people ! I never thought to hear that from you . :o

Hot air heating systems rely on the cold air return ductwork to pull the cold air from the room ,heat that air & return warm/hot air.
I ain't a physics or chemist or any letters behind my name...

BUT.... this is elementary stuff... warm air replacing the missing cold air.. :)

Have you never read the many threads about moving air ? I quote " it is easier to move cold air than it is to move hot air, move the cold air & hot air will replace it". That phrase has been repeated in many threads on here. :)

 
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Post by Lightning » Sat. Dec. 09, 2017 5:00 pm

windyhill4.2 wrote:
Sat. Dec. 09, 2017 2:12 pm
Hot air heating systems rely on the cold air return ductwork to pull the cold air from the room ,heat that air & return warm/hot air.
Are you reading what your writing? I think that's what I said too lol :lol:

Oh let me clarify, "return cold air to the furnace" lol

Apparently his warm air isn't mixing very well in the house, otherwise his room with the cold air return wouldn't be uncomfortably warm.

 
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Post by windyhill4.2 » Sat. Dec. 09, 2017 9:18 pm

He has 1, only 1 return air.... it is in the bedroom... obviously the t-stat is in another part of the house.
The warmest area in the house is going to be the area with the return air duct... in this case... the bedroom.

We ain't saying the same thing,nor are we agreeing.

 
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Post by David... » Sat. Dec. 09, 2017 9:35 pm

One of my systems has only one return and it is not too warm around the return grille. Try closing down the supplies for the room that is too warm.

David

 
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Post by windyhill4.2 » Sat. Dec. 09, 2017 9:47 pm

David... wrote:
Sat. Dec. 09, 2017 9:35 pm
One of my systems has only one return and it is not too warm around the return grille. Try closing down the supplies for the room that is too warm.

David
No one is saying that the return grill is too warm...

The room is too warm & it ain't going to matter if the supply vents are closed,moving all the cold air out fills the room with hot air.
The problem is that the hot room has the ONLY return grill in the house.

Of course there is the possibility that i can't read & i am the only one not understanding the issue.

 
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Post by Lightning » Sat. Dec. 09, 2017 9:49 pm

windyhill4.2 wrote:
Sat. Dec. 09, 2017 9:18 pm
He has 1, only 1 return air.... it is in the bedroom... obviously the t-stat is in another part of the house.
I clearly understand that part
windyhill4.2 wrote:
Sat. Dec. 09, 2017 9:18 pm
The warmest area in the house is going to be the area with the return air duct..
I completely disagree with that
windyhill4.2 wrote:
Sat. Dec. 09, 2017 9:18 pm
We ain't saying the same thing
Well then yer confused.
windyhill4.2 wrote:
Sat. Dec. 09, 2017 9:18 pm
,nor are we agreeing.
That is correct.


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